The type of recurrence used to determine the date of a holiday is specified at the top-left of the Type panel of the Recurrence Rules tab control. Q++Studio classifies recurring holidays into the following types (hint: use the Holiday Rule Wizard if you are unsure of the type of rule to use) :

Holiday rules that are based on a fixed Gregorian date, but not necessarily always occurring on the same date. An example is Christmas which is based on December 25th, but which may be moved to the following Monday in many countries, if December 25th falls on a Saturday or Sunday.

These are either holidays based on lunar events that occur after a given solar event has occurred. This is used for many lunisolar calendars of southeast Asia, where holidays fall on the Nth full moon after the beginning of the solar year (as they themselves define it). These are usually yearly events. Or they are holidays based on repeating lunar events, such as Ponga days in India and Sri Lanka. Then these are usually monthly events.

From the Type recurrence options tab, you can also specify the Observance of a holiday rule (for example, is it regional, religious, starts the evening before, ...), and additional recurrence options are available on the other recurrence options tabs.